problem with G-12 batch 05021702

Discussion in 'Rocket Boosted Gliders' started by burkefj, Dec 15, 2018.

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  1. Dec 15, 2018 #1

    burkefj

    burkefj

    burkefj

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    To anyone using G-12 32mm rocket motors, I flew a batch from 05021702 and it had two problems, the nozzle hole is supposed to be .104 one was .130, I replaced that with one from another batch from 2016 and flew them both, they both performed the same, about half the thrust and burned for 10-11 seconds instead of 8, I have both on video and flew four other nominal G-12's with the right nozzle also this morning and they boosted to around 500' instead of 150 with the first two. I contacted Karl but wanted to get the word out, I think they might have the wrong propellent in these, my model is heavy for a G-12 and I was barely able to keep it airborne, if you have any from that batch I'd send them to Karl or fly them in something very light, under 20 ounces.

    Frank
     
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  2. Dec 15, 2018 #2

    Steve Shannon

    Steve Shannon

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    If you haven’t already please submit MESS reports for these.
     
  3. Dec 15, 2018 #3

    burkefj

    burkefj

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    Mess filled out
     
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  4. Dec 17, 2018 #4

    georgegassaway

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    Many years ago, Aerotech made a batch of G12's that accidentally left out some ingredient that makes the propellant burn faster than regular Blue Thunder (same catalyst used for all the endburning engines like E6 andF10, IIRC). Thrust was about 2/3 of normal, burn time about 50% longer than normal. Wonder if history has repeated itself.

    Hmmm.... wonder if the 17 second burn "G7" uses a different formulation for a different burn rate and if so if that got used by mistake.

    We are not paying $$ for Newton-seconds, we are paying DEARLY for those special thrust curves that when wrong can destroy R/C RBG's.

    Also note that if the nozzle throat is larger than optimum, then the thrust will be lower and the burn time will go up since composite propellant burn rate varies depending on pressure (more pressure = faster burn & more thrust, lower pressure = longer burn & less thrust and also loss of N/Sec efficiency)

    On the other side, a few years ago Aerotech made some D7 reloads that burned TOO FAST, with a very rapid liftoff and acceleration, with about half the burn time. Launch was more like an E15. I had one S8E model actually shred the whole bolt-on horizontal stab off on boost, but was able to make it land without significant further damage as it had flaps I deployed to slow its nose-first dive and it landed into very tall grass.
     
  5. Dec 17, 2018 #5

    burkefj

    burkefj

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    I also had one batch of e6 motors where they accidentally used blackjack propellent, burned for 20 seconds, no thrust.
     
    Last edited: Dec 17, 2018
  6. Dec 31, 2018 #6

    JoeG

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    Thanks Frank. Will check my stock.
     

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